1. Field of the Invention
The present invention relates to a display apparatus and a method of controlling a picture of the display apparatus, and more particularly, to a display apparatus and a method of automatically controlling brightness and contrast of a screen of the display based on a luminance signal (e.g., a Y signal).
2. Description of the Related Art
In general, a display apparatus such as a TV decodes broadcasting signals transmitted from a broadcasting company to video signals to provide picture information to viewers. External video signal apparatuses such as a Video Tape Recorder (VTR) and a Digital Video Disc (DVD) are also used to transmit the video signals for the display apparatus. Such a display apparatus receives the video signals including a Y signal and a chrominance signal (e.g., an U/V signal) as an input from a source of the video signals, such as a broadcasting company, or an external video signal apparatus, and displays images using the input Y signal and the U/V signal.
A user may control contrast or brightness of an image, and screen size in a conventional display apparatus by means of a remote controller. Herein, the contrast and the brightness of displayed images are adjustable in response to an input control signal which is input through the remote controller.
FIGS. 1A, 1B and 1C illustrate a general waveform of the Y signal input to a conventional display apparatus. As shown in FIGS. 1A, 1B and 1C, a region f stores picture information of each frame, Sa indicates a saturation level, and CF is a cutoff level determining brightness of the Y signal. In a case of an ideal Y signal, an amplitude a of the region f is located between the saturation level Sa and the cutoff level CF.
However, the ideal Y signal is not often obtainable since the Y signal for the display apparatus varies depending on each of the broadcasting companies, a type of the video signals transmitted from each broadcasting company and the different types of video signals provided by the external video signal apparatuses. Thus, if the saturation level is exceeded or the signal level falls below the cutoff level, the display apparatus may encounter problems and display blurred images or images having some missing pixels.
As described above, the conventional display apparatus is inconvenient because the user must re-adjust the contrast or the brightness to optimize display settings if a channel and/or contents of the current display are changed, or if a DVD player or a VTR is used.